37 million people have already voted — here's what the data say

People vote at a polling station on the first day of early voting in Miami-Dade County for the general election, Monday, Oct. 24, 2016, in Miami. Associated Press/Lynne Sladky With just four days to go until Election Day, early voting data show that Hillary Clinton may have an advantage in the battleground state of Nevada, while Donald Trump carries more of an edge in Iowa.

States like Florida, North Carolina, and Ohio, on the other hand, are shaping up to be much tighter races.

At least 37 million people have already cast ballots, either in person or by mail, as of mid-day Friday, according to the US Elections Project, which is updated multiple times per day and run by University of Florida professor Michael McDonald.

A wave of early voting by Latinos is boosting expectations that Clinton will have a strong showing in states such as Arizona, Florida, and Nevada, the Washington Post reported on Thursday.

Early, in-person voting numbers among Latinos are "off the charts" in Florida, according to Daniel Smith, a University of Florida political science professor who runs the blog ElectionSmith. So far, 429,000 have voted in person — a 152% surge from this time in 2012.

Black turnout, however, has fallen in some states, leading to predictions that Clinton could lose some ground to Trump.

Earlier in the week, African-Americans accounted for just 15% of the early vote turnout — down from 25% — in Florida. Those numbers appear to be on the rise, however, possibly due to a visit from President Obama in Miami on Thursday.

Up to 40% of voters this year are expected to partake in early voting, according to Bloomberg. The surge in early voting is thought to benefit Clinton, as Republican voters historically vote on Election day in greater numbers than Democrats.

In the states where overall early voter turnout is down, such as Iowa and Ohio, Clinton's lead is less certain.

"I think both of those states are going to be razor thin come election night," McDonald told PBS Thursday evening.

In the battleground states, early, in-person voting is coming to a close, wrapping up Friday in Nevada, and over the weekend in North Carolina, Florida, and Ohio.